login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A193109 Least k such that 2^x + k produces primes for x=1..n and composite for x=n+1. 0
0, 1, 9, 3, 225, 15, 65835, 1605, 19425, 2397347205, 153535525935 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

All terms except the first four are congruent to 15 mod 30.

a(10) was found in 2005 by T. D. Noe and a(11) was found in the same year by Don Reble.

Other known values: a(13)=29503289812425.

LINKS

Table of n, a(n) for n=1..11.

MATHEMATICA

Table[k = 0; While[i = 1; While[i <= n && PrimeQ[2^i + k], i++]; i <= n || PrimeQ[2^i + k], k++]; k, {n, 9}] (* T. D. Noe, Jul 21 2011 *)

CROSSREFS

Another version of A110096.

Cf. A092506, A057733, A104070, A144487, A008597.

Sequence in context: A248311 A038293 A119516 * A242069 A197828 A116393

Adjacent sequences:  A193106 A193107 A193108 * A193110 A193111 A193112

KEYWORD

more,nonn

AUTHOR

Arkadiusz Wesolowski, Jul 21 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified December 22 16:00 EST 2014. Contains 252364 sequences.